The effects of ascorbate, 3-aminotriazole, and 1,3-bis-(2-chloroethyl)-1-nitrosourea on hydrogen peroxide levels in the rabbit aqueous humor.

3-aminotriazole (3-AT), a catalase inhibitor, given to pigmented rabbits in 0.2% drinking solution for 43 days, produced cataractous changes and over a 50% reduction in iris and ciliary process catalase activity. Aqueous H2O2 levels were suppressed by 60% which correlated with a 77% reduction in aqueous ascorbate concentration. Intravenous 3-AT at 1.0 g/kg body weight had no effect on either aqueous ascorbate or H2O2 levels. BCNU (1,3-bis-(2-chloroethyl)-1-nitrosourea) was given intravitreally to rabbits: 3.0 mg suppressed iris glutathione reductase activity by 80%, but only increased the oxidized glutathione/total glutathione ratio to 26% from 18%. Both aqueous ascorbate and H2O2 levels were unaltered at 48 hours. Buthionine sulfoximine (BSO) was given intravitreally; at 48 hours after 4.0 mg BSO, iris-ciliary body total glutathione levels were reduced by 80%, aqueous ascorbate levels were reduced by 53%, and aqueous H2O2 levels were unaltered. A direct correlation seems to exist between aqueous humor ascorbate and H2O2 concentrations, even during suppression of tissue catalase activity. Changes in glutathione status cause peroxide levels to be greater than predicted from the aqueous ascorbate concentration.